Performance of the LEP200 superconducting RF system

The LEP Superconducting RF system has reached its maximum configuration of 288 four-cell cavities powered by 36 klystrons. This has allowed the beam energy to be raised from 45.6 GeV where physics of the Z-particle was studied to well above 80.5 GeV the threshold of W pair production. The search for Higgs bosons and other new particles requires even higher beam energies. Currently the maximum operational energy achieved is 101 GeV with the RF system supplying a circumferential voltage of 3500 MV. This requires not only operating the cavities well beyond their design gradient but also demands a very high operational reliability from the entire system. The major developments necessary to achieve this performance are described

Operating Experience with the LEP200 Superconducting RF System

By the beginning of 1999, after several stages of installation, the RF system in LEP had gained a final total of 288 four-cell SC cavities. For 2000, the last year of LEP running, eight original LEP1 copper cavities were re-installed to bring their total to 56. During 1999 and 2000, the RF system was pushed to its absolute maximum limits for physics. By mid-2000 maximum total RF voltages of well over 3600 MV could be sustained, allowing beam energies of up to and even over 104 GeV for new particle searches. This corresponded to average gradients approaching 7.2 MV/m in the SC cavities, well above the design value of 6 MV/m. This level of performance was achieved due to the very successful high-field conditioning of the niobium-copper sputtered SC cavities, the many RF system improvements made in previous years and by a cryogenics system cooling power upgrade. Operation at very high energies however brought new difficulties, many related to the high fields and increased RF power levels. Running with the RF system at its limit required new operational procedures and facilities as well as constant follow up of cavity and RF system performance. LEP high energy running proved very successful, the beam energies and integrated luminosities obtained largely exceeded the most optimistic expectations. Finally, a vast amount of experience has been gained during the construction and operation of the LEP SC RF system. Some critical design issues in SC RF systems can be reviewed in the light of this experience

Ultimate Performance of the LEP RF System

The LEP Superconducting RF system reached its maximum configuration of 288 four-cell cavities powered by 36 klystrons in 1999. In 2000, this system, together with 56 cavities of the original copper RF system, routinely provided more than 3630 MV, allowing the beam energy to be raised up to 104.5 GeV. This not only required operating the cavities more than 15% above their design gradient, but has also demanded a very high operational reliability from the entire system. This paper will describe the operation of the LEP RF system during 2000, including new features, operational procedures and limitations

Progress in the Design of the SPL, an H−H ^{-} High-Intensity Linac at CERN

The SPL (Superconducting Proton Linac) is a 4 MW 2.2 GeV H- linac, intended to re-use most of the 352 MHz RF equipment from the decommissioned LEP machine. Injecting into the CERN PS, this linac would improve the intensity and quality of the CERN proton beams, while as a stand-alone facility could provide intense beams of radioactive ions or neutrinos (Neutrino Superbeam). Together with accumulator and compressor rings, it would be a suitable driver for a Neutrino Factory. Since the original proposal, many improvements to the design have been introduced, in order to simplify the layout and reduce costs. They include the reduction of the repetition frequency to 50 Hz, the design of a shorter superconducting (SC) linac section that goes up to the full energy with b=0.8 cavities, an improved DTL section including a new CCDTL design, a chopping line based on fast (2 ns rise time) low-voltage choppers and pulser, and a simplified front-end. Moreover, the problem of pulse mode operation of a superconducting linac with more than one cavity per klystron has been analysed in more detail, showing additional limitation but also proposing some possible compensation schemes